Charles’ LawCharles’ LawThe Temperature-Volume

Relationship

Charles’ LawCharles’ Law

• French chemist Jacques CharlesJacques Charles discovered that the volume of a gas at constant pressure changes with temperature.

• As the temperature of the gas increases, so does its volume, and as its temperature decreases, so does its volume.

C h a r l e s ’ L a wC h a r l e s ’ L a w

The law says that at constant pressure, the volume of a fixed number of

particles of gas is directly proportional to the absolute (Kelvin) temperature,

mathematically expressed as:

V = V = kkTT

Charles’ LawCharles’ Law

V = V = kkTTV = Volume

k = Charles’ Law constant of Proportionality

T = Temperature in Kelvins

ExplanationExplanation

• Raising the temperature of a gas causes the gas to fill a greater volume as long as pressure remains constant.

• Gases expand at a constant rate as temperature increases, and the rate of expansion is similar for all gases.

ExampleExample

• If the temperature of a given amount of gas is doubled, for example, its volume will also double (as long as pressure remains unchanged).

2V = 22V = 2kkTT

Charles’ LawCharles’ Law

Charles’ Law can be modified to a convenient form by solving

for k.

k k = V / T= V / T

Charles’ LawCharles’ Law

• In a sample with volume V1 & temperature T1, changing either volume or temperature converts these variables to V2 and T2.

VV11 / T / T1 1 = = k = k = VV2 2 / T/ T22

Therefore:

VV11 T T2 2 = V= V22 T T11

DemonstratioDemonstration of n of

Charles’ LawCharles’ Law

Charles’s law states that when a gas is kept at constant pressure, the volume of the gas will change with temperature.

In this experiment, balloons keep a small amount of gas (air) at an approximately constant pressure.

As the balloons are dipped into a beaker of liquid nitrogen (-196°C; -320°F), the air inside them quickly cools. The volume of the air inside the balloons decreases as the temperature of the balloons decreases.

As the balloons are dipped into a beaker of liquid nitrogen (-196°C; -320°F), the air inside them quickly cools. The volume of the air inside the balloons decreases as the temperature of the balloons decreases.

As the balloons are dipped into a beaker of liquid nitrogen (-196°C; -320°F), the air inside them quickly cools. The volume of the air inside the balloons decreases as the temperature of the balloons decreases.

As the balloons are dipped into a beaker of liquid nitrogen (-196°C; -320°F), the air inside them quickly cools. The volume of the air inside the balloons decreases as the temperature of the balloons decreases.

Relationship Relationship of Boyle’s Law of Boyle’s Law and Charles’ and Charles’

LawLaw

Temperature in kelvins

Pressuree in kilograms per square centimeter

Practical Practical ApplicationsApplications

Hot AIR BalloonHot AIR Balloon

The hot air that gives the hot-air balloon its name is commonly created by a

propane gas burner that sends powerful jets of flame into the colorful rip-stop nylon envelope. Once the balloon is

aloft, its height is maintained by opening and closing the blast valve, which controls the flow of the gas to the

burner.

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